Process for manufacturing ring-shaped member

ABSTRACT

A yield which is a ratio of the weight of a ring-shaped member to that of a stock material, and a yield which is a ratio of the ring-shaped member to a blank are improved, and the cost is reduced. In a method of producing a ring-shaped member in which a ring-shaped member is obtained from a longitudinally elongated annular blank  3 , a pair of linking portions  3   b,    3   c  are outward expanded from the inner side of the blank  3 , and a pair of arcuate portions  3   d  are pressed from the outer side toward the inner side to be pressingly expanded, thereby shaping into a ring-shaped member.

TECHNICAL FIELD

The present invention relates to a method of producing a ring-shaped member.

BACKGROUND ART

Conventionally, a ring-shaped member 1 such as shown in FIG. 9 is produced by a method in which, from a stock material 2 shown in FIGS. 11( a), (b) and having a predetermined thickness, a plurality of annular ring-shaped members 1 are punched out in a single or plural rows by a pressing apparatus.

In the conventional production method, however, the yield which is a ratio of the weight of the ring-shaped members 1 to that of the stock material 2 is poor, and hence the cost of the ring-shaped member 1 is increased. The reason is that the ratio of a skeleton S1 and a slug S2 to the ring-shaped member 1 is high in the material utilization. The term “skeleton” means a frame-like scrap which remains as a result of punching of the plurality of ring-shaped members 1. The term “slug” means a plurality of scraps which are removed by a punch in the process of punching out the plurality of ring-shaped members 1.

Therefore, a method of shaping a ring-shaped member shown in FIGS. 12( a), (b) has been proposed (for example, see Patent Literature 1).

The method of shaping a ring-shaped member disclosed in Patent Literature 1 above includes steps of: continuously bending the width of an oblong ring-like stock material while preventing it from being deformed, thereby forming the stock material into a circular shape; and shaping the circular stock material into a perfect circular shape.

As shown in FIG. 12( a), inner and outer rolls 103, 104 which are opposed and slidably clamp one width of the minor-axis side of an oblong ring-like stock material 100, and which are rotatable and movable, and a pair of bending rolls 105 which are movable are disposed. The inner and outer rolls 103, 104 are rotated in the direction of arrow F or the opposite direction, to feed the oblong ring-like stock material 100 in the direction of arrow L or the opposite direction. While performing the feeding, the pair of bending rolls 105 are pressed in the direction of arrow G, whereby a curvature process is gradually performed on a linear portion of the stock material 100 to shape a circular stock material 101.

As shown in FIG. 12( b), then, a large-diameter inner roll 106 is fitted onto the inner roll 103 so as to be simultaneously rotatable, and then internally in contact with the circular stock material 101. The large-diameter inner roll 106 and the outer rolls 103, 104 are rotated in the direction of arrow F or the opposite direction, whereby a ring-shaped member 102 which is shaped into a perfect circular shape can be obtained.

According to the method of shaping a ring-shaped member, the circular stock material 101 is obtained from the oblong ring-like stock material 100, and hence material utilization in which the ratio of a skeleton and a slug to the perfect circular ring-shaped member 102 is suppressed to be smaller than that of the skeleton S1 and the slug S2 to the ring-shaped member 1 described with reference to FIG. 11 is enabled. Therefore, the yield which is a ratio of the weight of the ring-shaped member 102 to that of the stock material is improved, and the cost of the ring-shaped member 102 can be reduced.

Patent Literature 1: Japanese Utility Model Application Laying-Open No. 62-203633 DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the method of shaping a ring-shaped member disclosed in Patent Literature 1, however, an arcuate portion 107 which remains in the circular stock material 101, and which has a small radius of curvature is pressingly expanded from the inner side by a strong pressing force in the direction of arrow K due to the large-diameter inner roll 106. When the arcuate portion 107 having a small radius of curvature is pressingly expanded from the inner side in this way, large “elongation” occurs in a radially inward region having a small radius of curvature and in the arcuate portion 107, so that the thickness is reduced and a stress is concentrated. In the process of shaping the circular stock material 101 into the perfect circular ring-shaped member 102, therefore, there is the possibility that the radially inward region of the arcuate portion 107 cracks. This impairs the yield which is a ratio of the perfect circular ring-shaped member 102 to the oblong ring-like stock material 100, and increases the cost.

The invention has been conducted in order to solve the problems. It is an object of the invention to provide a method of producing a ring-shaped member in which, although a yield that is a ratio of the weight of the ring-shaped member to that of a stock material can be improved to reduce the cost, a yield that is a ratio of the ring-shaped member to a longitudinally elongated annular blank can be improved.

Means for Solving the Problems

The invention will be described with reference to the reference numerals used in FIGS. 3 and 4, in order to facilitate the understanding of the contents of the invention. The invention provides a method of producing a ring-shaped member in which a ring-shaped member is obtained from a longitudinally elongated annular blank (3) having: a pair of arcuate portions (3 d) which are opposed to each other in ends in a longitudinally elongated direction; and a pair of linking portions (3 b, 3 c) which are opposed to each other in both sides in lateral directions perpendicular to the longitudinally elongated direction, and which link together terminals of the pair of arcuate portions (3 d), wherein the pair of linking portions (3 b, 3 c) are outward expanded from an inner side of the blank (3), and the pair of arcuate portions (3 d) are pressed from an outer side toward an inner side to be pressingly expanded, thereby shaping into a ring-shaped member.

According to the configuration, a ring-shaped member is obtained from the longitudinally elongated annular blank (3), and hence material utilization in which the ratio of a skeleton and a slug to the ring-shaped member is suppressed to a low level as compared with the case shown in FIG. 11 is enabled, and the yield that is a ratio of the weight of the ring-shaped member to that of a stock material can be improved.

Furthermore, at the same time when the pair of linking portions (3 b, 3 c) are outward expanded from the inner side of the longitudinally elongated annular blank (3), the pair of arcuate portions (3 d) are pressed from the outer side toward the inner side to be pressingly expanded, whereby the blank (3) is shaped into a ring-shaped member. Therefore, “elongation” in radially inward regions of the arcuate portions (3 d) in the both ends in the longitudinally elongated direction of the longitudinally elongated annular blank (3) is suppressed as far as possible, the thickness of the radially inward regions can be prevented from being locally reduced, and stress concentration in the radially inward regions is relaxed. As a result, the arcuate portions (3 d) in the both ends in the longitudinally elongated direction of the blank (3) can be prevented from cracking, and the yield which is a ratio of the ring-shaped member to the longitudinally elongated annular blank (3) can be improved.

The invention will be described with reference to the reference numerals used in FIGS. 3 to 6, in order to facilitate the understanding of the contents of the invention. The invention provides a method of producing a ring-shaped member in which a ring-shaped member is obtained from a longitudinally elongated annular blank (3) having: a pair of arcuate portions (3 d) which are opposed to each other in ends in a longitudinally elongated direction; and a pair of linking portions (3 b, 3 c) which are opposed to each other in both sides in lateral directions perpendicular to the longitudinally elongated direction, and which link together terminals of the pair of arcuate portions (3 d), wherein the pair of linking portions (3 b, 3 c) are outward expanded from an inner side of the blank (3), thereby shaping inflated linking portions (3B, 3C), the pair of arcuate portions (3 d) are pressed from an outer side toward an inner side to be pressingly expanded, thereby shaping enlarged arcuate portions (3D) having a radius of curvature which is larger than a radius of curvature of the arcuate portions (3 d), the pair of enlarged arcuate portions (3D) are then pressed from an outer side toward an inner side, thereby shaping enlarged arcuate portions (3E) having a radius of curvature which is larger than the radius of curvature of the enlarged arcuate portions (3D), and, while restricting lateral outward expansion, the pair of inflated linking portions (3B, 3C) are shaped into inflated linking portions (3F, 3F) having a radius of curvature which is smaller than a radius of curvature of the inflated linking portions (3B, 3C), thereby shaping into a ring-shaped member.

According to the configuration, a ring-shaped member is obtained from the longitudinally elongated annular blank (3), and hence material utilization in which the ratio of a skeleton and a slug to the ring-shaped member is suppressed to a low level as compared with the case shown in FIG. 11 is enabled, and the yield that is a ratio of the weight of the ring-shaped member to that of a stock material can be improved.

In the process of shaping the longitudinally elongated annular blank (3) into a ring-shaped member, at a same time when the pair of linking portions (3 b, 3 c) are outward expanded from the inner side of the blank (3), thereby shaping the inflated linking portions (3B, 3C), first, the pair of arcuate portions (3 d) are pressed from the outer side toward the inner side to be pressingly expanded, thereby shaping the enlarged arcuate portion (3D). Therefore, “elongation” in radially inward regions of the arcuate portions (3 d) in the both ends in the longitudinally elongated direction of the longitudinally elongated annular blank (3) is suppressed as far as possible, the thickness of the radially inward regions can be prevented from being locally reduced, stress concentration in the radially inward regions is relaxed, and the arcuate portions (3 d) in the both ends in the longitudinally elongated direction of the blank (3) can be prevented from cracking.

Furthermore, at a same time when the pair of enlarged arcuate portions (3D) are pressed from the outer side toward the inner side to be pressingly expanded, thereby shaping the enlarged arcuate portions (3E) having a radius of curvature which is larger than that of curvature of the enlarged arcuate portions (3D), while restricting lateral outward expansion, the pair of inflated linking portions (3B, 3C) are shaped into the inflated linking portions (3F, 3F) having a radius of curvature which is smaller than that of curvature of the inflated linking portions (3B, 3C), thereby shaping a ring-shaped member (1). Therefore, the arcuate portions (3 d) of the longitudinally elongated annular blank (3) can be prevented from cracking, and the yield which is a ratio of the ring-shaped member (1) to the longitudinally elongated annular blank (3) can be improved.

Particularly, the first step of shaping the linking portions (3 b, 3 c) of the blank (3) into the inflated linking portions (3B, 3C), and shaping the arcuate portions (3 d) into the enlarged arcuate portions (3D), and the second step of shaping the enlarged arcuate portions (3D) into the enlarged arcuate portions (3E) having a radius of curvature which is larger than that of the enlarged arcuate portions, and shaping the inflated linking portions (3B, 3C) into the inflated linking portions (3F, 3F) having a radius of curvature which is smaller than that of the inflated linking portions are performed to shape the ring-shaped member (1). While preventing the thickness of the radially inward regions of the arcuate portions (3 d) from being reduced, and preventing cracking from occurring, therefore, also the longitudinally elongated annular blank (3) which is thick can be shaped into a ring-shaped member having a shape such as an annular shape or a polygonal shape which is approximately annular.

EFFECTS OF THE INVENTION

According to the invention, by material utilization in which a ratio of a skeleton and a slug to the ring-shaped member is suppressed to a low level, the yield that is a ratio of the weight of the ring-shaped member to that of a stock material can be improved, and the cost of the ring-shaped member can be reduced. Moreover, “elongation” in the radially inward regions of the arcuate portions in the longitudinally elongated annular blank is suppressed as far as possible, the thickness of the radially inward regions can be prevented from being reduced, and stress is not concentrated in the radially inward regions. Therefore, cracking does not occur in the arcuate portions of the longitudinally elongated annular blank, and the yield which is a ratio of the ring-shaped member to the longitudinally elongated annular blank can be improved. Consequently, the invention is advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a first embodiment of a step of punching out blanks from a stock material.

FIG. 2 is a plan view showing a blank which is punched out from the stock material of FIG. 1.

FIG. 3 is a plan view showing an embodiment in a state where the blank is set in a first die pressing apparatus.

FIG. 4 is a plan view showing an embodiment of a ring-shaped member in a state where the ring-shaped member is shaped by the first die pressing apparatus.

FIG. 5 is a plan view showing an embodiment in a state where the ring-shaped member is set in a second die pressing apparatus.

FIG. 6 is a plan view showing an embodiment of a ring-shaped member in a state where the ring-shaped member is shaped by the second die pressing apparatus.

FIG. 7 is a plan view showing a second embodiment of the blank.

FIG. 8 is a plan view showing another embodiment of the step of punching out blanks from a stock material.

FIG. 9 is a plan view showing an example of the ring-shaped member.

FIG. 10 is a plan view showing a third embodiment of the blank.

FIG. 11 is a plan view showing of a conventional step of punching out blanks from a stock material, (a) shows single-row punching, and (b) shows parallel punching.

FIG. 12 is a view illustrating a method of shaping a ring-shaped member disclosed in Patent Literature 1.

DESCRIPTION OF REFERENCE NUMERALS

-   1, 1A ring-shaped member -   3, 27 longitudinally elongated annular blank -   3 b, 3 c linking portion -   3 d arcuate portion -   3D, 3E enlarged arcuate portion -   3B, 3C, 3F inflated linking portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the method of producing a ring-shaped member related to the invention will be described with reference to the drawings.

As shown in FIG. 1, while feeding a stock material 2 having a predetermined thickness in the longitudinal direction of the stock material 2 as indicated by arrow P, a plurality of longitudinally elongated annular blanks 3 are punched out in series by a pressing apparatus with being separated from each other by a predetermined gap 1 in the feeding direction. As the stock material 2, a bar member which is formed by shaping a metal such as copper, aluminum, iron, or stainless steel into a plate-like member by rolling or the like may be used, or a stock material which is originally formed into a plate-like shape may be used.

As shown in FIG. 2, each of the longitudinally elongated annular blanks 3 has a small longitudinally elongated hole 3 a having a width w1 in the inner side, and includes: a pair of arcuate portions 3 d, 3 d which are opposed to each other in both ends in the longitudinally elongated direction; and a pair of linear linking portions 3 b, 3 c which are respectively on both sides in the lateral direction perpendicular to the longitudinally elongated direction, to be opposed to each other, and which link together terminals of the pair of arcuate portions 3 d, 3 d.

As shown in FIG. 3, the longitudinally elongated annular blank 3 is set in a first die pressing apparatus 4. The first die pressing apparatus 4 includes a pair of right and left moving plates 5, a pair of front and rear shaping outer dies 8, and a pair of front and rear guiding plates 6. The pair of right and left moving plates 5 are reciprocated in the right and left directions (the directions of arrows X1, X2) by a reciprocating mechanism which is not shown, while being guided by the guiding plates 6. A shaping inner die 7 in which the projected plan view shape has a rear convex arcuate shape is upward protruded from the tip end of each of the right and left moving plates 5. The right and left shaping inner dies 7, 7 stand at positions which are bilaterally symmetrical about a line Y that is perpendicular to a line X, and their flat front faces meet each other. The width w2 of the meeting right and left shaping inner dies 7, 7 is set to a size which is slightly smaller than the width w1 of the longitudinally elongated hole 3 a of the blank 3, in order that the shaping inner dies can be fitted into the longitudinally elongated hole 3 a.

The pair of front and rear shaping outer dies 8 are reciprocated in the front and rear directions (the directions of arrows Y1, Y2) by a reciprocating mechanism which is not shown, while being guided by the guiding plates 6. A pressing face 8 a which is vertical upward protruded, and in which the projected plan view shape is recessed in an arcuate shape is provided in the tip end of each of the front and rear shaping outer dies 8. The radius of curvature of the pressing faces 8 a are set to a value which is larger than the radius of curvature of the outer circumferential faces of the arcuate portions 3 d of the longitudinally elongated annular blank 3.

The pair of front and rear shaping outer dies 8 are opposed to each other on the line Y, and placed at positions which are fore and aft symmetrical about the line X, and the opposing gap is set to a value which is larger than the dimension in the longitudinally elongated direction of the longitudinally elongated annular blank 3, in order that the longitudinally elongated annular blank 3 can be set.

As shown in FIG. 3, when the longitudinally elongated annular blank 3 is set in the first die pressing apparatus 4, an upper die 9 indicated by a dash-dot-dot line is lowered from the upper side. This causes the upper faces of the guiding plates 6, the pair of right and left shaping inner dies 7, and the pair of front and rear shaping outer dies 8 to be pressed by the lower face of the upper die 9. The upper faces of the blank 3, the shaping inner dies 7, and the shaping outer dies 8 are opposed to the lower face of the upper die 9 across a very small gap (a small gap which allows sliding motion), thereby preventing the blank 3 from vertically warping.

In this state, the right and left moving plates 5 are moved respectively toward the outer sides in the right and left lateral directions (the directions of arrows X1) perpendicular to the longitudinally elongated direction of the blank 3, and at the same time the front and rear shaping outer dies 8 are moved respectively toward the inner sides in the longitudinally elongated direction (the directions of arrows Y1). Then, the right and left shaping inner dies 7 press the linking portions 3 b, 3 c on the both sides in the right and left lateral directions of the longitudinally elongated annular blank 3, from the inner sides toward the outer sides (the directions of arrows X1) to, as shown in FIG. 4, expand the portions in the directions of arrows X1 at a uniform large radius of curvature, and the front and rear shaping outer dies 8 press the arcuate portions 3 d at the both ends in the longitudinally elongated direction of the blank 3, from the outer sides toward the inner sides (arrows Y1) in the longitudinally elongated direction of the blank 3, to expand the arcuate portions at a radius of curvature which is larger than that of the arcuate portions 3 d of FIG. 3. As a result, an oval annual ring-shaped member 1A such as shown in FIG. 4 is produced which has a pair of enlarged arcuate portions 3D having a radius of curvature that is larger than that of the arcuate portions 3 d of FIG. 3, and a pair of inflated linking portions 3B, 3C that are continuous to the enlarged arcuate portions, and that are arcuately inflated and curved at a large radius of curvature.

As described above, the plurality of longitudinally elongated annular blanks 3 are punched out from the stock material 2 shown in FIG. 1, and the longitudinally elongated annular blanks 3 are shaped by the first die pressing apparatus 4, thereby producing the ring-shaped member 1A shown in FIG. 4. By the material utilization in which a ratio of the skeleton S1 and the slug 2 of FIG. 1 to the ring-shaped member 1A is suppressed to be lower than that of the skeleton S1 and the slug 2 to the ring-shaped member 1 described with reference to FIG. 11, therefore, the yield that is a ratio of the weight of the ring-shaped member 1 to that of the stock material 2 can be improved, and the cost of the ring-shaped member 1A can be reduced.

Furthermore, the linking portions 3 b, 3 c on the both sides in the right and left lateral directions of the longitudinally elongated annular blank 3 are pressed from the inner sides to the outer sides in the right and left lateral directions (the directions of arrows X1) to be expanded in the directions of arrows X1 as shown in FIG. 4, and at the same time pressed from the outer sides in the longitudinally elongated direction of the blank 3 toward the inner sides (the directions of arrows Y1) to be expanded at a radius of curvature which is larger than that of the arcuate portions 3 d, whereby “elongation” in the radially inward regions which have a small radius of curvature, and which are in the arcuate portions 3 d of the blank 3 is suppressed as far as possible, and the thickness of the radially inward regions can be prevented from being reduced. Moreover, a flow of the material which, on the contrary, may cause the arcuate portions 3 d to be thickened is produced, and stress concentration in the radially inward regions is relaxed. As a result, cracking does not occur in the arcuate portions 3 d, and the yield which is a ratio of the ring-shaped member 1A to the longitudinally elongated annular blank 3 can be improved.

From the state of the first die pressing apparatus 4 shown in FIG. 4, the right and left shaping inner dies 7 are further moved in the directions of arrows X1 to expand the linking portions 3 b, 3 c of the blank 3 from the inner sides, and the front and rear shaping outer dies 8 are moved in the directions of arrows Y1 to expand the arcuate portions 3 d of the blank 3, whereby shaping to a shape which is more approximated to an annular shape than the ring-shaped member 1A seen in FIG. 4 can be performed.

In the case where the longitudinally elongated annular blank 3 is a thick blank, or in the case where the ring-shaped member 1A shown in FIG. 4 is shaped more surely to a shape which is more approximated to an annular shape, furthermore, the ring-shaped member is set to a second die pressing apparatus 11 shown in FIG. 5 in the next step.

The second die pressing apparatus 11 includes a pair of front and rear shaping outer dies 12, and a pair of right and left restricting dies 13. The shaping outer dies 12 are reciprocated in the front and rear directions (the directions of arrows Y1, Y2) by a reciprocating mechanism which is not shown, while being guided by guiding plates 14, and the restricting dies 13 are reciprocated in the right and left directions (the directions of arrows X1, X2) by a reciprocating mechanism which is not shown, while being guided by the guiding plates 14.

Each of the pair of front and rear shaping outer dies 12 includes a placing face 12 a, and a pressing face 12 b which is vertically upward protruded from the placing face 12 a, and in which the projected plan view shape is recessed in an arcuate shape. The radius of curvature of the pressing face 12 b is set to a value which is larger than that of the outer circumferential face of the enlarged arcuate portion 3D in the ring-shaped member 1A shown in FIG. 4, and the pressing face 12 b is formed into an arcuate shape which extends along a part of the circumferential face of the ring-shaped member 1 having an annular shape shown in FIG. 6 or a polygonal shape that is approximately annular. In each of the pair of right and left restricting dies 13, a restricting face 13 a in which the projected plan view shape is recessed in an arcuate shape is formed in the end face of the side that is opposed to the counter restricting die, the radius of curvature of the restricting face 13 a is set to a value which is smaller than the radius of curvature of the outer circumferential faces of the inflated linking portions 3B, 3C in the ring-shaped member 1A shown in FIG. 4, and the pressing face 12 b is formed into an arcuate shape which extends along a part of the circumferential face of the ring-shaped member 1 having an annular shape shown in FIG. 6 or a polygonal shape that is approximately annular.

As shown in FIG. 5, when the ring-shaped member 1A is set in the second die pressing apparatus 11 in a state where the inflated linking portions 3B, 3C in the ring-shaped member 1A are clamped by the right and left restricting dies 13 and the enlarged arcuate portions 3D in the ring-shaped member 1A and the vicinities of the portions are placed on the placing faces 12 a of the shaping outer dies 12, an upper die 15 indicated by a dash-dot-dot line is lowered from the upper side. This causes the upper faces of the ring-shaped member 1A, the shaping outer dies 12, and the restricting dies 13 are opposed to the lower face of the upper die 15 across a very small gap (a small gap which allows sliding motion), thereby preventing the ring-shaped member 1A from vertically warping.

In this state, the shaping outer dies 12 are moved in the directions of arrows Y1. Then, the pressing faces 12 b of the shaping outer dies 12 press the enlarged arcuate portions 3D in the ring-shaped member 1A from the outer sides toward the inner sides to expand the portions at a large radius of curvature. This causes the radially outer faces of the enlarged arcuate portions 3D of the ring-shaped member 1A to be pressed by the arcuately recessed pressing faces 12 b of the shaping outer dies 12 from the outer sides toward the inner sides. Therefore, the enlarged arcuate portions are deformed along the pressing faces 12 b, and, as shown in FIG. 6, enlarged arcuate portions 3E having a radius of curvature which is larger than the radius of curvature of the enlarged arcuate portions 3D are shaped. In the radially outward portions of the enlarged arcuate portions 3E, “elongation” occurs, and “elongation” in the radially inward regions is suppressed as far as possible, so that the thickness of the radially inward regions can be prevented from being reduced. Moreover, a flow of the material which, on the contrary, may cause the enlarged arcuate portions 3E to be thickened is produced, and stress concentration in the radially inward regions is relaxed. As a result, cracking does not occur in the enlarged arcuate portions 3E.

At the same time when the enlarged arcuate portions 3E are shaped, the inflated linking portions 3B, 3C in the ring-shaped member 1A shown in FIG. 5 are expanded in the directions of arrows X1. At this time, the outer faces of the inflated linking portions 3B, 3C butt against the arcuately recessed restricting faces 13 a of the restricting dies 13, whereby the ring-shaped member 1A is deformed along the restricting faces 13 a while restricting the ring-shaped member from being excessively expanded in the directions of arrows X1. Therefore, the inflated linking portions 3B, 3C in the ring-shaped member 1A shown in FIG. 4 are shaped into inflated linking portions 3F, 3F having a radius of curvature which is smaller than that of the inflated linking portions 3B, 3C. As a result, the annular ring-shaped member 1 such as shown in FIGS. 6 and 9 in which the enlarged arcuate portions 3E and the inflated linking portions 3F are continuous to each other is produced.

In the process of shaping into the annular ring-shaped member 1, “elongation” in the radially inward regions of the enlarged arcuate portions 3D and the inflated linking portions 3B, 3C is suppressed as far as possible, the thickness of the radially inward regions can be prevented from being reduced, and stress concentration in the radially inward regions is relaxed. As a result, the ring-shaped member 1 can be produced without cracking the enlarged arcuate portions 3D and the inflated linking portions 3B, 3C. Therefore, the yield which is a ratio of the ring-shaped member 1 to the longitudinally elongated annular blank 3 can be improved.

In the above-described embodiment, as shown in FIG. 2, the longitudinally elongated annular blank 3 in which the width w1 of the longitudinally elongated hole 3 a is small is punched out, and the blank 3 is produced into a ring-shaped member. Alternatively, as shown in FIG. 7, a longitudinally elongated annular blank 27 having an oval longitudinally elongated hole 27 a in which the width w3 is sufficiently larger than the width w1 of FIG. 2 may be punched out, and the blank 27 may be shaped into a ring-shaped member in the same procedure as the above-described embodiment. Also in this case, in the same manner as the above-described embodiment, the yield which is a ratio of the ring-shaped member to the longitudinally elongated annular blank 27 can be improved, and the cost of the ring-shaped member can be reduced.

In the case where a plurality of longitudinally elongated annular blanks 3, 27 are punched out from the stock material 2 having a predetermined width, as shown in FIG. 8( a), (b), the outer end faces of the pair of linear linking portions 3 b, 3 c in the longitudinally elongated annular blanks 3, 27 can be formed by using both end faces 2 a in the width direction of the stock material 2, and the pair of arcuate portions 3 d which cause the pair of linear linking portions 3 b, 3 c to be continuous to each other can be formed in both end portions in the longitudinal direction by sharing the stock material 2 with a pressing apparatus. According to the configuration, material utilization in which a ratio of scraps to the longitudinally elongated annular blanks 3, 27 is suppressed to the minimum level is enabled. Namely, the scraps are reduced to the slug S1 which is punched away in the process of punching the longitudinally elongated hole 3 a or the oval longitudinally elongated hole 27 a, and drum-shaped end plate portions 2 x which exist between the longitudinally elongated annular blanks 3 or blanks 27 that are arranged in the longitudinal direction, and that are cut off from the stock material 2, as indicated by the hatched lines in FIG. 8( a), (b). As a result, the yield which is a ratio of the weight of the ring-shaped members 1 to that of the stock material 2 can be further improved.

In the longitudinally elongated annular blanks 3, 27, the linking portions 3 b, 3 c which link together the terminals of the pair of arcuate portions 3 d, 3 d are not restricted to those which are formed into a linear shape as shown in FIG. 2, and, for example, may be formed into a non-linear shape configured by lines of flexure as shown in FIG. 10. The longitudinally elongated annular blanks 3, 27 may be obtained by a pressing process such as cutting or punching on a bar member made of a metal, forging, or the like, in place of the process of performing punching on the plate-like stock material 2 as shown in FIG. 1. 

1. A method of producing a ring-shaped member in which a ring-shaped member is obtained from a longitudinally elongated annular blank having: a pair of arcuate portions which are opposed to each other in ends in a longitudinally elongated direction; and a pair of linking portions which are opposed to each other in both sides in lateral directions perpendicular to the longitudinally elongated direction, and which link together terminals of said pair of arcuate portions, wherein said pair of linking portions are outward expanded from an inner side of said blank, and said pair of arcuate portions are pressed from an outer side toward an inner side to be pressingly expanded, thereby shaping into a ring-shaped member. A method of producing a ring-shaped member in which a ring-shaped member is obtained from a longitudinally elongated annular blank having: a pair of arcuate portions which are opposed to each other in ends in a longitudinally elongated direction; and a pair of linking portions which are opposed to each other in both sides in lateral directions perpendicular to the longitudinally elongated direction, and which link together terminals of said pair of arcuate portions, wherein said pair of linking portions are outward expanded from an inner side of said blank, thereby shaping inflated linking portions, said pair of arcuate portions are pressed from an outer side toward an inner side to be pressingly expanded, thereby shaping enlarged arcuate portions having a radius of curvature which is larger than a radius of curvature of said arcuate portions, said pair of enlarged arcuate portions are then pressed from an outer side toward an inner side, thereby shaping enlarged arcuate portions having a radius of curvature which is larger than the radius of curvature of said enlarged arcuate portions, and, while restricting lateral outward expansion of said pair of inflated linking portions, said pair of inflated linking portions are shaped into inflated linking portions having a radius of curvature which is smaller than a radius of curvature of said inflated linking portions, thereby shaping into a ring-shaped member. 